The present invention relates to a liquid crystal display device and more particularly to a liquid crystal display device of active matrix type using thin film transistors (TFTs) or the like.
In a liquid crystal display device of the active matrix type, non-linear devices (e.g., switching devices) are disposed in a manner to correspond to a plurality of pixel electrodes arranged in a matrix array. The liquid crystal in each pixel is always in a driven state, in principle, (at a duty ratio of 1.0). In comparison with the so-called "simple matrix type" device, which employs a time division driving system, therefore, the active system has better contrast and, therefore, has become indispensable, particularly in a color liquid crystal display device. A typical example of the switching devices is a thin film transistor (TFT).
FIG. 21 is a cross section of a gate terminal portion of a conventional active matrix type liquid crystal display device. As shown in the figure, a transparent glass substrate SUB1 has silicon oxide films SIO deposited on the upper and lower surfaces thereof. On the upper silicon oxide film SIO a gate terminal GTM consisting of an aluminum film g and a transparent conductive film (Indium-Tin-Oxide (ITO): nesa film) dl is formed. On the lower silicon oxide film SIO a polarizing plate POLl is formed.
A liquid crystal display device of the active matrix type using thin film transistors is described in Japanese Patent Laid-Open No. 309921/1988 or on pp. 193 to 210 of Nikkei Electronics is an article entitled "Active Matrix Type Color Liquid Crystal Display of 12.5 Type Adopting Redundant Construction" published on Dec. 15, 1986 by NIKKEI McGRAW-HILL, for example.